Patent GB-401798-A (GB)
Title: Improvements in electrical selective systems
IPC: H02J13/00
Filed: 1932-07-01
Abstract: 401,798. Distant control systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and CHRISTIAN, D. A., Morven, Charlton Road, Charlton, both in London. July 1, 1932, No. 18624. [Class 40 (i).] The selecting switch of an electric selective system, such as a telephone system, remote control system &c. is also adapted to act as a call finder, and is driven by an alternating current synchronous motor. Fig. 1 shows the circuit arrangements of the switch and Fig. 3 shows the cam equipment for operating the switch contacts. Fig. 4 shows an exchange equipment for use with the switch when employed in a telephone system. Switch operation and construction, Figs. 1 and 3. The switch is adapted for continuous operation by a self-starting synchronous motor MD, the contacts 1-12 being closed and opened successively by the cams CA1, CA2. A relay A is included in one line wire B connecting the switch to the control point and the arrangement is such that when any set of contacts 1-12 corresponding to a subscriber's line connected thereto is in a calling condition the relay A is operated to open the circuit of the motor MD and thereby bring the switch to rest on the appropriate contacts. The cam CA3 and contacts C maintain the motor circuit closed until the switch is correctly positioned. A relay B connected in series with a rectifier BR is connected across the line wires A, B when the switch CS occupies position 1 and is responsive to current of reverse polarity in the line wires for initiating the operation of the switch as a selector instead of a call finder. Relay B operates a trigger tr4, Fig. 3, into the region of operation of a cam CA4 which lifts a contact operating member bsp on to a cam surface bcr so as to maintain contacts bc1, bc2 closed until the switch passes through position 12 and consequently maintains relay B connected across the line wires. When the switch arrives at contacts associated with a wanted subscriber, relay B is operated by reverse current from the control point and the motor circuit is opened to bring the switch to rest. In the off-normal position of the switch, relay B also brings contacts bd1, bd2 into operative relation with one of the projections a-j on cam CA5 and these contacts are maintained closed until the switch again passes position 12. Contacts bd1 switch relay R across the line wires instead of relay B. When the selected connection is to be broken down, relay R is operated by reverse current from the control point to again operate the motor and opens the line wires at contacts r<1>, r<2> so that as the switch is driven to normal extension lines passed over shall not interfere with the apparatus. In position 12 contacts bc1, bc2, bd1, bd2 are released and the switch continues to operate as a call finder. Telephone equipment, Fig. 4. The equipment shown may be extended by a line finder operating on terminals A1, B 1, P 1, M 1, or may be selected by a final selector FS operating on terminals A2, B2, 12. Incoming calls. Normally the line polarity is such that + ve is supplied to line A leading to the switch CS over relay D(ii) and-ve to line B over relays D(i) and Q. When the switch CS, Fig. 1, in the course of one of its revolutions encounters a subscriber line which is in a calling condition, relays A, Q are operated, the relay A stopping the motor and Q operating relays BB, C, to place a guard on P2 of selector FS and connect dial tone to the line wire A. The subscriber whose line is thus extended to the equipment of Fig. 4, then dials his own number to impulse relay Q, which at contact q1 operates the magnet ASDM to step the switch AS on to contacts appropriate to the calling subscriber. During dialling relay A at the switch is maintained operated as its release is retarded by the short-circuiting effect of the rectifier AR. At the end of impulsing, relay C releases to remove dial tone and operates relay CO. Relay CO reverses the battery connections to the line wires at contacts col, co2 and thereby effects release of relay A to restart the motor MD. As soon as the switch CS moves from the calling line, relays Q, BB release. When the switch CS reaches position 1, relay B is connected across line and is operated due to reverse current, together with relay Q. Relay B stops the motor and Q again operates BB which brings about the release of Q, B, the latter restarting the motor MD. Relay BB also effects operation of motor ME, Fig. 4, which then rotates in synchronism with the motor MD. The motor ME operates contacts sm4-sm6 successively and when the contact sm corresponding to the selected contact in the bank of wiper AS2 is operated relay T is operated. Relay T brings motor ME to rest and releases relay CO to reestablish to original line condition and cause operation of relay A to stop the motor MD. The motors are thus brought to rest in positions corresponding to the calling extension. Relays D, Q also are operated to pull up start relay ST of the line finders, one of which hunts for the calling line, the line being marked at P1, in a circuit including relay K. When the line is found, K operates to connect line wires A, B to finder wires A1, B1 and the subscriber's meter M over wiper AS4. Metering can now be effected in any suitable manner. Relays BB, T, D, Q also are released so that the connection is now dependent upon relay F, i.e. upon the calling subscriber maintaining a loop on wires A1, B1. Release. When the calling subscriber hangs up his receiver, earth is removed from P1 and relay K is released to open the meter circuit, disconnect the line wires A, B from the finder. wires A1, B1 and close the circuit of motor ME which drives to normal and closes a homing circuit for switch AS. Release of relay A by the calling subscriber, restarts the motor MD which then continues to rotate. Outgoing calls. Connection is first made by a suitable final selector to the control point apparatus, Fig. 4 at the terminals A2, B2, P2, the test circuit being completed over relays P2, CO. Relay CO reverses the battery connection to the line wires and brings about the operation of relay AA. When switch CS, Fig. 1, reaches position 1 relay B is operated by the reverse current and the switch is brought to rest. Impulses received over the final selector, impulse relay AA which steps the switch AS into a position dependent upon the wanted subscriber. When dialling is completed relay AA is held operated and relay C released to release CO. Relay CO releases Q, B, and closes a circuit for the motor ME, the release of B also restarting motor MD. The motors MD, ME rotate synchronously until when motor ME operates contacts sm corresponding to the selected contact in bank AS2, relay T is operated to stop further rotation of motor ME and operate relay CO to reverse the line condition and thereby operate relay B to stop motor MD. Relay CO also effects operation of relay TT which at contacts tt5, tt6 connects ringing current to the line wires A, B and at tt10 connects ringing tone to the calling subscriber. Relay TT also releases CO which restores the line conditions. Connection is now made with the called extension. When the called subscriber replies, relay F is operated to remove ringing tone from wire B2 and ringing current from line wires A, B and at contacts f5, f6 reverse the line connection to prepare for the operation of relay R, Fig. 1. Release. When either party to the connection hangs up his receiver the apparatus is restored. If the calling subscriber hangs up contact z is opened and if the called party hangs up d2 is opened and in either case relay AA is released. Release of AA brings about restoration of switch ASDM, and releases F which restores the line connections and causes the motor ME to drive to normal when its circuit is opened at contacts sm1. Restoration of the line connections effects operation of R, Fig. 1, which closes the circuit of motor MD. When the switch CS arrives in position 1 relay R releases and the system is restored to normal operating condition. The Provisional Specification states that if the operation of the selecting switch CS b comes faulty and continuous rotation is prevented, the circuits connected to the contacts of the switch are automatically connected in parallel to the control point in order that calls although collective may still be effected.